Phytotoxicity and allelopathic impact of Impatiens glandulifera

The knowledge of how invasive species spread in a new environment might be important for their management control. Moreover, biochemical interaction underlies the novel weapon hypothesis thus presenting one of numerous explanations for species invasiveness. This study aimed to determine the total phenolics content in various parts of I. glandulifera and evaluate their phytotoxicity on the germination of monocot and dicot species. Phytotoxicity and allelopathic activity of worldwide invasive Impatiens species (Balsaminaceae) I. glandulifera (originated in the Himalayas) on wheat and rapeseed germination and seedling growth was assessed ex situ at Aleksandras Stulginskis University in 2016. The phenolic content ranged between 0.615 and 7.566 mg g–1 in Impatiens extracts, however, it significantly inhibited germination and seedling growth of the recipient species. Seed germination and seedling emergence are the outcomes of a sequence of biological events initiated by water imbibition followed by enzymatic metabolism of storage nutrients. The recorded germination rate was different for each recipient species. Inhibition of Impatiens extracts was recorded stronger for rapeseed germination (11.5– 81%) than that for wheat germination (71–86.5%), possibly due to different seed coat anatomy and thus its permeability. Therefore the strongest inhibition (86.5%) was recorded for rapeseed germination (11.5%) in 0.2% fruit + seed extract of I. glandulifera. Mean length of wheat hypocotyl (14.2 mm) and radicle (4.4 mm) exhibited a weaker response to the extract of I. glandulifera than rapeseed (4.4 mm and 1.4 mm, respectively). Consequently, recruitment and regeneration of native species might be negatively affected by the invasive Impatiens species in invaded habitats.